Effects of Foliage Spraying with Sodium Bisulfite on the Photosynthesis of <em>Orychophragmus violaceus</em>

• Main Authors: Zhongying Li, Yanyou Wu, Deke Xing, Kaiyan Zhang, Jinjin Xie, Rui Yu, Tian Chen, Rongrong Duan
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: Horticulturae
• Subjects: agricultural production; redox; photorespiration; chlorophyll fluorescence; dose effect
• Online Access: https://www.mdpi.com/2311-7524/7/6/137

Sulphurous acid derived from sulfur dioxide (SO₂) emission leads to the pollution of irrigation water and the inhibition of plant growth. The safe concentration threshold of NaHSO₃ in plants should be clarified to promote agricultural production. In this study, <i>Orychophragmus violaceus</i> seedlings were used as experimental materials and five NaHSO₃ concentrations (i.e., 0, 1, 2, 5, 10 mmol·L⁻¹) were simultaneously sprayed on the leaf surface of different seedlings separately. Leaf physiology responses under different concentrations were analyzed. The NaHSO₃ did not promote photosynthesis in <i>O. violaceus</i> under the 1 and 2 mmol·L⁻¹ treatments. It was conducive to the net photosynthetic rate (<i>P_N</i>), photorespiration rate (<i>R_p</i>), chlorophyll content, actual photochemical quantum yield (Y_II) and photochemical quenching (qP) under the 5 mmol·L⁻¹ treatment. However, quantum yield of regulated energy dissipation (Y_NPQ) and nonphotochemical quenching (NPQ) were inhibited. Under the 10 mmol·L⁻¹ treatment, <i>P_N</i>, chlorophyll content, Y_II, qP, dark respiration rate (<i>R_d</i>) and electron transport rate (ETR) showed significant decreases, while the photorespiration portion (<i>S_p</i>) significantly increased. Our results demonstrated that NaHSO₃ provided a sulfur source for plant growth and interfered with the redox reaction of the plant itself, and its role as a photorespiratory inhibitor might be masked.